Improper input validation in Apache HTTP Server
Priority HIGH 73CWE-20Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.0 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-399 and the CVSS impact.
Summary
The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the Protocols configuration includes h2 or h2c, does not restrict request-header length, which allows remote attackers to cause a denial of service (memory consumption) via crafted CONTINUATION frames in an HTTP/2 request.
Why it matters now
EPSS 0.7907 99th percentileScored 2026-11-07
Public exploit Yes 2 exploit referencesTagged by NVD and the CNA
Fix Fixed Red Hat: 4 advisories
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Apache | Apache HTTP Server | 2.4.17 - 2.4.23 | — | No fix listed | CNA |
- Apache HTTP Server VendorApache Affected 2.4.17 - 2.4.23 Fixed in — No fix listed CNA
CPE configurations NVD · 7
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:apache:http_server:2.4.17:*:*:*:*:*:*:* | 2.4.17 | Vulnerable | Apache |
| cpe:2.3:a:apache:http_server:2.4.18:*:*:*:*:*:*:* | 2.4.18 | Vulnerable | Apache |
| cpe:2.3:a:apache:http_server:2.4.19:*:*:*:*:*:*:* | 2.4.19 | Vulnerable | Apache |
| cpe:2.3:a:apache:http_server:2.4.20:*:*:*:*:*:*:* | 2.4.20 | Vulnerable | Apache |
| cpe:2.3:a:apache:http_server:2.4.21:*:*:*:*:*:*:* | 2.4.21 | Vulnerable | Apache |
| cpe:2.3:a:apache:http_server:2.4.22:*:*:*:*:*:*:* | 2.4.22 | Vulnerable | Apache |
| cpe:2.3:a:apache:http_server:2.4.23:*:*:*:*:*:*:* | 2.4.23 | Vulnerable | Apache |
- cpe:2.3:a:apache:http_server:2.4.17:*:*:*:*:*:*:* Versions 2.4.17 Vulnerable ·Apache
- cpe:2.3:a:apache:http_server:2.4.18:*:*:*:*:*:*:* Versions 2.4.18 Vulnerable ·Apache
- cpe:2.3:a:apache:http_server:2.4.19:*:*:*:*:*:*:* Versions 2.4.19 Vulnerable ·Apache
- cpe:2.3:a:apache:http_server:2.4.20:*:*:*:*:*:*:* Versions 2.4.20 Vulnerable ·Apache
- cpe:2.3:a:apache:http_server:2.4.21:*:*:*:*:*:*:* Versions 2.4.21 Vulnerable ·Apache
- cpe:2.3:a:apache:http_server:2.4.22:*:*:*:*:*:*:* Versions 2.4.22 Vulnerable ·Apache
- cpe:2.3:a:apache:http_server:2.4.23:*:*:*:*:*:*:* Versions 2.4.23 Vulnerable ·Apache
Remediation
Red Hat 4 advisories
- RHSA-2017:1413 Released 2017-06-07 · Red Hat rating ImportantRed Hat JBoss Core Services Apache HTTP Server 2.4.23 Service Pack 1 for RHEL 7
- Red Hat JBoss Core Services on RHEL 7 Server jbcs-httpd24-httpd-2.4.23-120.jbcs.el7, jbcs-httpd24-httpd-devel-2.4.23-120.jbcs.el7, jbcs-httpd24-httpd-libs-2.4.23-120.jbcs.el7 +13
- RHSA-2017:1414 Released 2017-06-07 · Red Hat rating ImportantRed Hat JBoss Core Services Apache HTTP Server 2.4.23 Service Pack 1 for RHEL 6
- Red Hat JBoss Core Services on RHEL 6 Server jbcs-httpd24-httpd-2.4.23-120.jbcs.el6, jbcs-httpd24-httpd-devel-2.4.23-120.jbcs.el6, jbcs-httpd24-httpd-libs-2.4.23-120.jbcs.el6 +13
- RHSA-2017:1415 Released 2017-06-07 · Red Hat rating ImportantRed Hat JBoss Core Services Apache HTTP Server 2.4.23 Service Pack 1
- Red Hat JBoss Core Services
Show 1 more Red Hat advisories
- RHSA-2017:1161 Released 2017-04-26 · Red Hat rating Moderatehttpd24-httpd security, bug fix, and enhancement update
- Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 6) httpd24-httpd-2.4.25-9.el6, httpd24-httpd-devel-2.4.25-9.el6, httpd24-httpd-manual-2.4.25-9.el6 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) httpd24-httpd-2.4.25-9.el7, httpd24-httpd-devel-2.4.25-9.el7, httpd24-httpd-manual-2.4.25-9.el7 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.7) httpd24-httpd-2.4.25-9.el6, httpd24-httpd-devel-2.4.25-9.el6, httpd24-httpd-manual-2.4.25-9.el6 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.3) httpd24-httpd-2.4.25-9.el7, httpd24-httpd-devel-2.4.25-9.el7, httpd24-httpd-manual-2.4.25-9.el7 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 6) httpd24-httpd-2.4.25-9.el6, httpd24-httpd-devel-2.4.25-9.el6, httpd24-httpd-manual-2.4.25-9.el6 +5
- Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) httpd24-httpd-2.4.25-9.el7, httpd24-httpd-devel-2.4.25-9.el7, httpd24-httpd-manual-2.4.25-9.el7 +5
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat JBoss Core Services | Fixed | RHSA-2017:1415 |
| Red Hat JBoss Core Services on RHEL 6 Server | Fixed | RHSA-2017:1414 |
| Red Hat JBoss Core Services on RHEL 7 Server | Fixed | RHSA-2017:1413 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 6) | Fixed | RHSA-2017:1161 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) | Fixed | RHSA-2017:1161 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 6.7) | Fixed | RHSA-2017:1161 |
| Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.3) | Fixed | RHSA-2017:1161 |
| Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 6) | Fixed | RHSA-2017:1161 |
| Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) | Fixed | RHSA-2017:1161 |
Not affected: 9 products
- Red Hat Directory Server 8
- Red Hat Enterprise Linux 5
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat JBoss Enterprise Application Platform 5
- Red Hat JBoss Enterprise Application Platform 6
- Red Hat JBoss Enterprise Web Server 1
- Red Hat JBoss Enterprise Web Server 2
- Red Hat JBoss Web Server 3
Timeline
- 2026-10-02 Threatist record created from CVE-2016-8740
- 2026-10-03 Alias added: GHSA-pfj2-72r3-p693
References
Exploit 2
Other 18
- https://support.apple.com/HT208221
- https://www.tenable.com/security/tns-2017-04
- https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03725en_us
- https://security.netapp.com/advisory/ntap-20180423-0001/
- [httpd-cvs] 20190815 svn commit: r1048743 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.html
- [httpd-cvs] 20190815 svn commit: r1048742 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.html
- [httpd-cvs] 20200401 svn commit: r1058586 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.html
- [httpd-cvs] 20200401 svn commit: r1058587 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/vulnerabilities-httpd.xml security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.html
- [httpd-cvs] 20210330 svn commit: r1073139 [1/13] - in /websites/staging/httpd/trunk/content: ./ security/json/
- [httpd-cvs] 20210330 svn commit: r1073140 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/cvejsontohtml.py security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.html
- [httpd-cvs] 20210330 svn commit: r1888194 [10/13] - /httpd/site/trunk/content/security/json/
- [httpd-cvs] 20210330 svn commit: r1073139 [10/13] - in /websites/staging/httpd/trunk/content: ./ security/json/
- [httpd-cvs] 20210330 svn commit: r1073149 [1/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/
- [httpd-cvs] 20210330 svn commit: r1073146 [3/3] - in /websites/staging/httpd/trunk/content: ./ security/cvejsontohtml.py security/vulnerabilities-httpd.xml security/vulnerabilities_22.html security/vulnerabilities_24.html
- [httpd-cvs] 20210330 svn commit: r1073149 [10/13] - in /websites/staging/httpd/trunk/content: ./ security/ security/json/
- [httpd-cvs] 20210603 svn commit: r1075360 [3/3] - in /websites/staging/httpd/trunk/content: ./ security/json/CVE-2021-31618.json security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.html
- [httpd-cvs] 20210606 svn commit: r1075467 [2/2] - in /websites/staging/httpd/trunk/content: ./ security/json/CVE-2021-31618.json security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.html
- [httpd-cvs] 20210606 svn commit: r1075470 [4/4] - in /websites/staging/httpd/trunk/content: ./ security/json/CVE-2020-13938.json security/vulnerabilities_13.html security/vulnerabilities_20.html security/vulnerabilities_22.html security/vulnerabilities_24.html
More Apache Http Server vulnerabilities
- TI-2021-18535 Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773) KEVCVSS 3.1CRITICAL 9.8
- TI-2021-18417 Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 KEVCVSS 3.1CRITICAL 9.8
- TI-2024-25716 Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path. KEVCVSS 3.1CRITICAL 9.1
- TI-2021-17490 mod_proxy SSRF KEVCVSS 3.1CRITICAL 9.0
- TI-2019-00184 Use after free in Apache HTTP Server KEVCVSS 3.1HIGH 7.8
- TI-2009-03392 The TLS protocol, and the SSL protocol 3.0 and possibly earlier, as used in Microsoft… CVSS 3.1CRITICAL 9.8
Sources
- CVE-2016-8740 · CVE Program
- CVE-2016-8740 · NVD
- FIRST EPSS
- GHSA-pfj2-72r3-p693 · GitHub Advisory Database · CC BY 4.0
- CVE-2016-8740 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences